Drive unit for motor vehicles

ABSTRACT

The invention relates to a drive unit for motor vehicles, comprising an internal combustion engine, a transmission which is mounted downstream therefrom and is provided with an integrated differential, and a separating clutch that is disposed between the internal combustion engine and the transmission. The differential is driven via a bevel wheel and a bevel-gear drive comprising a drive pinion on an output shaft of the transmission. In order to create a drive unit that is advantageous regarding structure and efficiency, the bevel wheel ( 48 ) of the differential ( 16 ) is placed laterally from the separating clutch ( 26 ) from a vertical perspective and partly protrudes (A) therefrom in an axial direction.

The invention relates to a drive unit for motor vehicles according tothe preamble of claim 1.

Such a drive unit which is installed lengthwise, with a front axledifferential which is integrated into the change speed gearbox, isdisclosed by EP 1 120 587 A1 for example. Here the differential ofconventional design is positioned in the axial direction behind theseparating clutch which is located on the crankshaft of the internalcombustion engine, yielding a specific overhang of the internalcombustion engine which is defined by way of the axes of rotation of thedriven front wheels of the motor vehicle and yielding a correspondingweight distribution. It is within the scope of structural conditions totry to dimension the indicated overhang as small as possible.

DE 34 18 557 C2 furthermore discloses a drive unit in which thedifferential is located in front of the separating clutch in the axialdirection; however this solution entails considerable structuralcomplexity, due for example to the significant lateral offset of theoutput shaft of the change speed gearbox which drives the differential,and by one axle shaft of the differential having to be routed throughthe oil pan of the internal combustion engine.

The object of the invention is to propose a drive unit of the generictype which with only little additional construction effort permitsshortening of the drive unit, particularly of the distance between theengine/gearbox flange and the axle differential, or makes possible anadditional installation space for clutch-side powertrain parts.

This object is achieved as claimed in the invention with thecharacterizing features of claim 1. The solution can be used both forfront-wheel drive and also for rear-wheel drive. Advantageousdevelopments of the invention are described by the other claims.

As claimed in the invention, it is proposed that the ring gear of thedifferential as viewed from a vertical perspective is mounted laterallyfrom the separating clutch and projects partly over it in the axialdirection. With the proposal as claimed in the invention the drive unitis significantly shortened and the differential with the outgoing axleshafts is advantageously displaced forward, by which the indicatedoverhang is reduced and a more uniform weight distribution of the motorvehicle is achieved. Alternatively the installation space gained in theaxial direction can be used for example for additional installation of astarter-generator device.

In one advantageous development of the invention the differential casecomprising the axle bevel gears and planet gears can also be positionedlaterally next to the separating clutch. This results in that at theminimally necessary lateral offset of the output shaft of the changespeed gearbox the separating clutch and the ring gear with differentialcase can be positioned next to one another and can be operated withoutadversely affecting their function.

The separating clutch can advantageously be a multidisk friction clutchof conventional design which is small in radial extent. The multidiskfriction clutch can be a wet or dry friction clutch, a two-disk dryclutch, for example, with a diameter reduced proportionally to theincreased friction surface.

Furthermore, the differential housing of the differential of the changespeed gearbox can be built partly around the separating clutch, theflywheel of the internal combustion engine which bears the separatingclutch projecting radially over the ring gear. Thus an especiallyadvantageous “internested” design is produced in which the flywheel ofthe internal combustion engine with the starter gear rim for the startercan remain essentially unchanged structurally, while the separatingclutch is modified accordingly.

Furthermore, the differential housing can be designed especiallyadvantageously in part by the adjoining housing of the internalcombustion engine and/or the integral housing cover which laterallycovers the differential can also partly cover the housing of theinternal combustion engine. In addition to a structure which isespecially well-suited to casting, this results in additional stiffeningof the drive unit in the area of the screw connection between theinternal combustion engine and the adjoining differential which isintegrated into the housing of the change speed gearbox.

An embodiment is also possible in which the integral housing coverroughly overlaps the engine flange and the housing cover in thelongitudinal direction of the gearbox is braced by means of boltsrelative to the engine flange (by means of bolting).

The change speed gearbox can furthermore have a shaft configuration withan input shaft and an output shaft which bears the drive pinion fordriving the differential. This yields an especially advantageous gearboxdesign of simple structure with favorable transmission efficiency due toreduced engagement of teeth; a third shaft, for example a countershaft,can be omitted accordingly. The drive pinion is dimensioned so that anexactly defined, predetermined distance between the input shaft and theoutput shaft can be set.

Here the input shaft and the output shaft can be aligned for example soas to be axially parallel. In one alternative embodiment the input shaftand the output shaft can run obliquely to one another at least inindividual areas, so that the drive pinion and the ring gear of thedifferential are designed for example as beveloid gears so that theoutput shaft runs in the direction toward the input shaft. Thus thedistance between the input shaft and the output shaft can be reduced,and this measure can additionally lead to keeping the length of thegearbox short. That is, depending on the desired distance between theinput shaft and the output shaft, either the diameter of the drivepinion is chosen to that effect, the drive pinion and the ring gear canbe made as beveloid gears, or a combination of the two in the changespeed gearbox can be implemented.

In particular, for an axially parallel execution of the input shaft andthe output shaft, the axial distances between the input shaft and theoutput shaft can be advantageously increased proportionally to produce alarge lateral offset. Moreover radial enlargement of the correspondinggear sets optionally makes possible a further reduction in the overalllength of the change speed gearbox, even if it does not affect theindicated reduction of the overhang. On the other hand, by reducing theaxial distance by for example a “longer” bevel gear, for example alarger drive pinion, and the concomitant reduction of the distancebetween the input shaft and the output shaft however a shorterspeed-transforming transmission can be achieved, if this is desirable.

Furthermore, one axle shaft of the differential can advantageouslyextend below the input shaft of the change speed gearbox and to theother output side of the differential in the axial direction closelyfollowing the separating clutch. Furthermore, the output shaft can bepivot mounted laterally in relation to the input shaft so that theindicated axle shaft intersects the input shaft closely below or aboveit. These measures contribute both to an optimum shortening of the driveunit which is possible within the scope of structural conditions andalso to improved ground clearance of the motor vehicle.

One embodiment of the invention is described below with further details.

The attached drawings are in diagrammatic form wherein

FIG. 1 shows a front drive unit for motor vehicles with an internalcombustion engine which is only suggested, a partially illustratedchange speed gearbox with an integrated differential and a multi-diskfriction clutch in a top view;

FIG. 2 shows a side view of the housing cover of the differential in thearea of the separating plane between the internal combustion engine andthe change speed gearbox;

FIG. 2 a shows a side view of the housing cover of the differential inthe area of the engine flange between the internal combustion engine andthe change speed gearbox;

FIG. 3 shows the configuration of the differential, the gearbox shaftsand the multidisk friction clutch as shown in FIG. 1, but without theillustrated housing sections;

FIG. 4 shows the configuration as shown in FIG. 3 in a viewcorresponding to the arrow X.

FIG. 1 shows in highly schematic form a front drive unit 10 which can beinstalled lengthwise in a motor vehicle, with an internal combustionengine 12 which is only suggested, and a downstream change speed gearbox14 with an integrated differential 16. The indicated components aredescribed only to the extent that this is necessary for this invention;otherwise the components can be of the design known to one skilled inthe art or can correspond to the prior art.

A flywheel 20 with a flywheel sprocket 22 shrink-fitted onto thecircumferential side is attached to the crankshaft 18 of the internalcombustion engine 12. The crankshaft 18 is pivot mounted in the housing24 of the internal combustion engine 12 in a manner which is not shown.

On the flywheel 20 of the internal combustion engine 12 there is amultidisk friction clutch 26 as a separating clutch, which in thisexemplary embodiment is a double dry friction clutch of conventionaldesign with two friction disks 28. The clutch actuation is not thesubject matter of the invention and therefore is not shown. As a resultof the two friction disks 28 the separating clutch 26 can be madesmaller or with a smaller outside circumference in the radial direction,with an identical or even larger drive transmission output compared forexample to a single-disk dry friction clutch.

The housing 30 of the change speed gearbox 14 in the illustratedvertical separating plane 32 is flanged to the housing 24 of theinternal combustion engine 12, the housing section 30 a of thedifferential 16 integrated into the housing 30 being made in a manneryet to be described.

The change speed gearbox 14 is a conventional transmission with severalgears, for the sake of simplified representation only the gear sets withthe gears 34, 35, and 38, 40 being shown for the first and secondforward gear of the change speed gearbox 14. For the sake of form itshould be emphasized that an axle or shaft of the change speed gearboxfor accommodating a reverse gear wheel for the reverse gear of thechange speed gearbox 14 is not included in the shaft configuration to bedescribed.

The gears 34, 38 (and others) sit on the input shaft 42 and the gears36, 40 (and others) sit on the output shaft 44 of the change speedgearbox 14. The gear sets 34, 36 and 38, 40 can be activated by way ofsynchronizer clutches (not shown) for shifting the transmission ratiosor gears of the change speed gearbox 14.

Furthermore, the output shaft 44 bears a drive pinion 46 which mesheswith a ring gear 48 of the bevel gear differential 16. The differential16 in the conventional manner drives two axle half shafts 52, 54 whichare pivot mounted in the differential housing 30 a by way of axle bevelgears and planet gears (not shown) which are supported in thedifferential case 50. While the axle half shaft 52 which is shown on theleft in the drawings is routed only through the large housing cover 56of the differential 16, the right half axle shaft 54, crossing the inputshaft 42 of the change speed gearbox 14, extends as far as the opposinghousing section of the differential housing 30i al . In the conventionalmanner the drive shafts (not shown) which drive the front wheels of themotor vehicle are connected to the axle half shafts 52, 54.

The input shaft 42 and the output shaft 44 can run so as to be axiallyparallel, as shown in FIGS. 1 and 3. If a shorter distance (section C,FIG. 3) is required between the input shaft 42 and the output shaft 44for a certain gearbox design, on the one hand the pinion diameter of thedrive pinion 46 can be increased and/or on the other hand the drivepinion 46 and the ring gear 48 of the differential 16 can each be madefor example as beveloid gears. The latter measure results in that thenthe output shaft 44′ runs obliquely in the direction to the input shaft42; this is shown schematically by the broken line in FIG. 1. With knownjoint pieces (not shown) the output shaft 44′ can be moved again into anaxially parallel alignment of the input shaft 42 when the desireddistance between the input shaft 42 and the output shaft 44′ is reached.

As is to be seen in the drawings in FIGS. 1 and 2, the large housingcover 56 of the differential 16 can extend forward beyond the indicatedseparating plane 32 between the engine housing 24 and the housing 30 ofthe change speed gearbox 14 so that the integral housing cover 56projects over the engine housing 24 in sections and is screwed to thelatter and to the housing section 30 a of the differential 16 (compareFIG. 2, generally with screws designated as 58).

According to another embodiment, the housing cover 56′ of thedifferential 16′ can overlap the flange 240 of the drive unit 24. Indoing so, connecting means 560, 561 which are inserted lengthwise intothe housing cover 56′, for example long screws, can be connected(screwed) to the flange 240 of the drive unit 24 (FIG. 2 a).

As FIGS. 1, 3, and 4 show, the differential case 50 which holds the axlebevel gears and planet gears (not shown) and the ring gear 48 of thedifferential 16 are positioned laterally next to the separating clutch26, and the lateral offset of the differential which is necessary forthis purpose can be kept smaller by the reduced outside circumference ofthe separating clutch 26. Due to the lateral offset in turn thedifferential 16 can be shifted forward to a greater extent (to the leftin FIG. 1), the ring gear 48 projecting in the axial direction over theseparating clutch 26 by the section A which is shown in FIG. 3.

Furthermore, as shown in FIG. 1, the differential housing 30 a of thedifferential 16 of the change speed gearbox 14 is built partly aroundthe separating clutch 26, the flywheel 20 which bears the separatingclutch 26 with the sprocket ring 22 of the internal combustion engine 12projecting radially over the ring gear 48 by the amount B which is shownin FIG. 3.

Due to the above described, not overly large lateral offset of thedifferential 16, furthermore the change speed gearbox 14 can be madewith only two axially parallel shaft configurations or with only theinput shaft 42 and the output shaft 44 which bears the pinion 46 fordriving the differential 16. This means that a third shaft, for examplea countershaft, for achieving the required axial distance between theinput shaft 42 and the output shaft 44 can be omitted.

Here the gears 34, 36 and 38, 40 (and other gears) are enlarged indiameter for the transmission ratios of the change speed gearbox 14 forachieving the require lateral offset of the differential 16 and theaxial distance between the input shaft 42 and the output shaft 44,optionally with the stipulated transmission ratios unchanged. Optionallythe gears 34, 36 and 38, 40 and other speed gears can be reduced inwidth by the increase of the diameter so that an increase of therotating masses of the change speed gearbox 14 can be avoided and itsoverall length can be reduced.

The longer axle shaft 54 of the differential 16, as is especiallyapparent in FIG. 4, extends at a short distance s₁ below the input shaft42 of the change speed gearbox 14 and closely following the separatingclutch 26 (compare distance s₂ in FIG. 3) to the other output side ofthe differential 16.

Finally, the output shaft 44 of the change speed gearbox 14, as can beseen especially in FIG. 4, is pivot mounted laterally in relation to theinput shaft 42 so that the indicated axle shaft 54 as described aboveintersects the input shaft 42 closely below the latter (distance s₁).

The invention is not limited to the described embodiment. Thus, insteadof shifting the differential 16 forward, the acquired installation spacecan also be used for additional installation of a starter-generatordevice by means of which the internal combustion engine 12 is started inthe conventional manner and optionally the motor vehicle can beelectrically driven by way of the change speed gearbox 14 and/or thevehicle electrical system can be supplied with current in generatoroperation.

1. Drive unit for motor vehicles comprising: an internal combustionengine, a downstream change speed gearbox with an integrated axledifferential, and a separating clutch mounted between the internalcombustion engine and the change speed gearbox, the differential beingdriven by way of a bevel gear with a drive pinion on an output shaft ofthe change speed gearbox, and a ring gear, wherein the ring gear of thedifferential as viewed from a vertical perspective is mounted laterallyfrom the separating clutch and so as to projecting partly over it in theaxial direction.
 2. The drive unit as claimed in claim 1, wherein adifferential case of the differential holding the axle bevel gears andplanet gears is positioned laterally next to the separating clutch. 3.The drive unit as claimed in claim 1, wherein the separating clutch is amultidisk friction clutch small in radial extent.
 4. The drive unit asclaimed in claim 1, wherein the differential housing of the differentialof the change speed gearbox is built partly around the separatingclutch, and the flywheel of the internal combustion engine which bearsthe separating clutch projecting radially over the ring gear.
 5. Thedrive unit as claimed in claim 1, wherein the differential housing isformed in part by an adjoining housing of the internal combustion engineand wherein the integral housing cover which laterally covers thedifferential also partly covers the housing of the internal combustionengine.
 6. The drive unit as claimed in claim 1, wherein the integralhousing cover which laterally covers the differential partly overlapsthe engine flange and the gearbox is connected to the drive unit,connecting means, preferably long screws, being inserted roughlylengthwise in relation to the longitudinal axis of the gearbox under theoutline of the housing cover and effecting connection to the engineflange.
 7. The drive unit as claimed in claim 1, wherein the changespeed gearbox has a shaft configuration with an input shaft and anoutput shaft which bears the drive pinion for driving-the differential,the drive pinion being dimensioned so that a predetermined distanceseparates the input shaft from the output shaft.
 8. The drive unit asclaimed in claim 7, wherein the input shaft and the output shaft arealigned so as to be axially parallel.
 9. The drive unit as claimed inclaim 7, wherein the output shaft extends from the drive pinion area andat least in individual areas in the direction of the input shaft for thepurpose of increasing reduction of the distance between the input shaftand the output shaft.
 10. The drive unit as claimed in claim 7, whereinthe axial distances between the input shaft and the output shaft areincreased proportionally to produce a large lateral offset.
 11. Thedrive unit as claimed in claim 10, wherein the gear wheels for thetransmission ratios of the change speed gearbox are enlarged to achievethe large lateral offset between the input shaft and the output shaft.12. The drive unit as claimed in claim 7, wherein an axle shaft of thedifferential extends below the input shaft of the change speed gearboxand at a short distance toward the other output side of the differentialis connected to the separating clutch.
 13. The drive unit as claimed inclaim 7, wherein the output shaft is pivot mounted laterally in relationto the input shaft so that the respective axle shaft intersects theinput shaft a short distance below the latter.